Low-grade fibromyxoid sarcoma (LGFMS) and hybrid sclerosing epithelioid fibrosarcoma (SEF)/LGFMS have a low potential for recurrence (10%) and metastasis (5%) but they are notorious for late occurring metastases. The aim of this study was to evaluate the outcome of LGFMS and review similar cases reported in the literature. We retrospectively evaluated 24 LGFMS operated at a single Institution. All cases were histologically revised. Mean age was 34 years (range, 8 to 74). Two cases presented areas of SEF (hybrid tumours). Three patients presented with metastasis at diagnosis. A strong cytoplasmic staining for MUC4 antibody was found in the majority of neoplastic cells. RT-PCR was feasible in 6 cases and it detected the presence of FUS-CREB3L2 fusion gene chimeric transcript. Mean follow-up was 44 months (range, 6 to 217). Two patients developed lung metastasis after 9 and 26 months respectively. Low-grade fibromyxoid sarcoma has a various histopathologic spectrum with few cases of LGFMS that share histopathologic resemblance with SEF, thereby reinforcing a possibility of a link within these two. It is of paramount importance an accurate and extensive sampling and examination of the whole specimen, in order to identify higher risk patients.

Among women in Taiwan, thyroid cancer is the fifth most common malignant neoplasia. However, genomic profiling of papillary thyroid cancer (PTC) cases from Taiwan has not been attempted previously. We used whole-exome sequencing to identify mutations in a cohort of 19 PTC patients. Sequencing was performed using the Illumina system; Sanger sequencing was used to validate all identified mutations. We identified new somatic mutations in APC, DICER1, LRRC8D and NDRG1. We also found somatic mutations in ARID5A, CREB3L2, MDM4, PPP2R5A and TFPT; mutations in these genes had been found previously in other tumors, but had not been described previously in PTC. We also investigated the pathway deregulation in BRAF-mutated PTC compared with wild-type BRAF PTC. In checking our gene mutations against The Cancer Genome Atlas (TCGA) database, we identified aberrations in one pathway that are specific to BRAF-mutated PTC: maturity-onset diabetes of the young. In addition, the caffeine metabolism pathway showed aberrations that are specific to wild-type BRAF PTC. For this study, we performed a comprehensive exome-wide analysis of the mutational spectra of Taiwanese patients with PTC. We identified novel genes that are potentially associated with PTC tumorigenesis, as well as aberrations in pathways that led to the distinct pathogeneses of BRAF-mutated PTC and wild-type BRAF PTC, which may provide a new target for PTC therapy.

Low-grade fibromyxoid sarcoma (LGFMS) and sclerosing epithelioid fibrosarcoma (SEF) are rare tumors with distinct sets of morphological features, both characterized by MUC4 immunoreactivity. Tumors exhibiting features of both entities are considered hybrid LGFMS-SEF lesions. While the majority of LGFMS cases are characterized by FUS-CREB3L2 gene fusions, most cases of pure SEF show EWSR1 gene rearrangements. In the largest study of hybrid LGFMS-SEF tumors to date, all cases exhibited FUS rearrangements, a similar genetic profile to LGFMS. We herein describe the clinicopathological features and genetic findings of a case of primary renal hybrid LGFMS-SEF occurring in a 10-year-old child, with disseminated metastases. Fusion gene detection using a next-generation sequencing-based anchored multiplex PCR technique (Archer FusionPlex Sarcoma Panel) was performed on both the primary renal tumor that showed the morphology of a LGFMS, and a cervical metastasis that showed the morphology of SEF. An EWSR1-CREB3L1 gene fusion occurring between exon 11 of EWSR1 and exon 6 of CREB3L1 was present in both the LGFMS and SEF components. This unusual case provides evidence that a subset of hybrid LGFMS-SEF harbor EWSR1-CREB3L1 gene fusions. In this case, these features were associated with an aggressive clinical course, with disease-associated mortality occurring within 12 months of diagnosis.

We report the case of a sclerosing perineurioma with conspicious collagen rosette formation in a 20-year-old male presenting with a firm, painless nodule on the palmar side of his right ring finger. The main differential diagnosis is a low-grade fibromyxoid sarcoma. The distinction between these entities is important because low-grade fibromyxoid sarcoma has a metastatic potential, while, as a rule, perineuriomas are benign. The presence of collagen rosettes in this current case makes this distinction even more difficult given that approximately 30% of low-grade fibromyxoid sarcoma cases show the focal presence of collagen rosettes. The demonstration of the characteristic t(7;16), t(11;16) or t(11;22) translocations (resulting in the FUS-CREB3L2, FUS-CREB3L1 or EWSR1-CREB3L1 fusion genes, respectively) or immunoreactivity for MUC4, a recently described sensitive and specific marker for low-grade fibromyxoid sarcoma, remain the gold standard in the diagnosis of low-grade fibromyxoid sarcoma, differentiating it from perineurioma. This case is, to our knowledge, the first report on collagen rosettes in sclerosing perineurioma, extremely well mimicking low-grade fibromyxoid sarcoma, and further expanding the morphological spectrum of this rare subtype of perineurioma.

Low-grade fibromyxoid sarcoma (LGFMS) is a bland spindle cell neoplasm that typically arises in the deep soft tissues of the proximal extremities or trunk of young adults. The majority of LGFMS are characterized by a recurrent (7;16)(q34;p11) translocation, resulting in the FUS-CREB3L2 fusion gene, which generates a chimeric protein with transcriptional regulatory activity. Small numbers harbor a FUS-CREB3L1 fusion resulting from t(11;16)(p11;p11), whilst rare cases harbor the EWSR1-CREB3L1 fusion. LGFMS is of low to moderate cellularity and consists of bland spindle cells with small, angulated nuclei and scant, wispy cytoplasm, arranged in a whorled growth pattern and typically showing abrupt transition from myxoid to fibrous areas. Immunohistochemical expression of MUC4 is a consistent finding. Hyalinized spindle cell tumor with giant rosettes (HSCTGR) is a morphological variant of LGFMS that shares the same balanced translocation, and is also immunoreactive for MUC4. A potential relationship between LGFMS and sclerosing epithelioid fibrosarcoma (SEF), a rare fibroblastic neoplasm that most commonly arises in the deep soft tissues of the lower extremities, limb girdles or trunk, has also been suggested. SEF is classically composed of nests and cords of epithelioid cells with clear or eosinophilic cytoplasm embedded within densely sclerotic stroma. In some cases, areas indistinguishable from LGFMS are present, and these have been shown to contain FUS-CREB3L2 fusion transcripts. The majority of pure SEF tumors harbor EWSR1 rearrangements, with EWSR1-CREB3L1 and more rarely EWSR1-CREB3L2 gene fusions more common than those involving FUS. MUC4 immunoreactivity is also seen in approximately 70% of SEF. Surgical resection of these tumors with clear margins is the treatment of choice. Correct diagnosis is important because of the significant potential for recurrence and late metastatic spread. We review LGFMS and SEF, discussing morphology and immunohistochemistry, genetics and molecular findings, and the differential diagnosis.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare, malignant fibroblastic neoplasm, morphologically composed of cords, nests or sheets of monotonous epithelioid cells within a collagenous matrix. It has been recently characterized by recurrent pathogenic EWS-CREB3L1/2 or FUS-CREB3L2 fusions and common MUC4 protein expression by immunohistochemistry. Typically SEF occur in middle-aged adults and rarely have been reported within the abdominal cavity. Here we report an 18-year-old man with intraabdominal tumor and multiple disseminated liver metastases, presenting pure SEF histologic and immunophenotypic features. Fluorescence in situ hybridization analysis showed unbalanced rearrangement of Ewing sarcoma breakpoint region 1 (EWSR1) gene. Genomic profiling by array CGH, followed by RT-PCR and sequencing analysis, revealed a previously not reported EWSR1 translocation partner, cAMP-responsive element-binding protein 3-like 3 (CREB3L3). The novel EWSR1-CREB3L3 fusion further extends the range of fusion types involving EWSR1 that are characteristic for SEF.

We report the case of a 55-year-old woman who developed a mass in the soft tissue of the anterior right proximal thigh. Microscopic findings in the biopsy specimen supported the diagnosis of sclerosing epithelioid fibrosarcoma (SEF). This entity is part of a spectrum of lesions that includes low-grade fibromyxoid sarcoma (LGFMS) and hyalinizing spindle cell tumor with giant rosettes (HSCTGR). It shares with LGFMS occasional overlapping histopathologic features and immunopositivity for MUC4. Although FUS and CREB3L2 gene rearrangements, characteristics of LGFMS, have been found in hybrid tumors (those with features of both SEF and LGFMS) and in examples of LGFMS with relapses showing SEF morphology, it appears that EWSR1 and CREB3L1 rearrangements predominate over FUS and CREB3L2 rearrangements among "pure" SEF tumors. Recent information about SEF is briefly reviewed.

Endogenous bornavirus-like nucleoprotein elements (EBLNs) have been discovered in the genomes of various animals including humans, whose functions have been seldom studied. To explore the biological functions of human EBLNs, we constructed a lentiviral vector expressing a short-hairpin RNA against human EBLN1, which successfully inhibited EBLN1 expression by above 80% in infected human oligodendroglia cells (OL cells). We found that EBLN1 silencing suppressed cell proliferation, induced G2/M phase arrest, and promoted apoptosis in OL cells. Gene expression profiling demonstrated that 1067 genes were up-regulated, and 2004 were down-regulated after EBLN1 silencing. The top 10 most upregulated genes were PI3, RND3, BLZF1, SOD2, EPGN, SBSN, INSIG1, OSMR, CREB3L2, and MSMO1, and the top 10 most-downregulated genes were KRTAP2-4, FLRT2, DIDO1, FAT4, ESCO2, ZNF804A, SUV420H1, ZC3H4, YAE1D1, and NCOA5. Pathway analysis revealed that these differentially expressed genes were mainly involved in pathways related to the cell cycle, the mitogen-activated protein kinase pathway, p53 signaling, and apoptosis. The gene expression profiles were validated by using quantitative reverse transcription polymerase chain reaction (RT-PCR) for detecting these 20 most-changed genes. Three genes closely related to glioma, RND3, OSMR, and CREB3L2, were significantly upregulated and might be the key factors in EBLN1 regulating the proliferation and apoptosis of OL cells. This study provides evidence that EBLN1 plays a key role in regulating cell life and death, thereby opening several avenues of investigation regarding EBLN1 in the future.

Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft-tissue neoplasm with a deceptively benign histological appearance and low-grade malignant potential which is often mistaken for other reactive or benign lesions. It most frequently harbors balanced t(7;16) translocation, and leads to the fusion of the FUS and CREB3L2 genes which can be detected by cytogenetic methods. Young adults are most commonly affected and it typically arises in the deep proximal extremities or trunk with frequent recurrences. It may metastasize to the lungs several years later. Paravertebral LGFMS is exceedingly rare and only few cases have been published in the literature. In those cases the novel immunohistochemical markers and cytogenetic studies were not performed and morphological mimickers could not be confidently excluded.We present a rare case of paravertebral LGFMS from a 54-years-old male patient, which previously was misdiagnosed as a neurofibroma with subsequent tumor recurrence. The concrete diagnosis was established by using MUC4 immunohistochemical stain and fluorescent in situ hybridization (FISH), which showed diffuse membranous positivity and supernumerary ring chromosome with unbalanced FUS gene rearrangement, respectively. The latter finding is also rare and may cause diagnostic dilemma if one is not aware of such uncommon, but well-documented phenomenon. Differential diagnosis with other low-grade spindle cell tumors will also be discussed along with the literature review.

Low-grade fibromyxoid sarcoma is a rare soft tissue tumor with a benign histologic appearance but comparatively aggressive clinical course. These discrepant features make it extremely important to diagnose early so that appropriate management can be initiated. This diagnosis often hinges on the presence of the hallmark cytogenetic aberration, a balanced 7;16 translocation resulting in a FUS-CREB3L2 fusion gene. Although this neoplasm most commonly arises in the deep soft tissue of the lower extremities, it has been reported to arise from a wide variety of sites including intraabdominal and intracranial locations. Only 1 previous study has described low-grade fibromyxoid sarcoma as arising from a bony site; however, cytogenetic and immunohistochemical confirmation was not available at that time. Herein, we describe the first ever cytogenetically confirmed case of low-grade fibromyxoid sarcoma arising as a primary bone tumor in the tibia of a 35-year-old woman.

Low-grade fibromyxoid sarcoma (LGFMS) is a deceptively bland malignancy with potential for late recurrence and metastasis, which usually occurs in the deep soft tissues of the extremities and trunk. Most LGFMSs harbor a characteristic gene fusion of FUS-CREB3L2, and recently MUC4 immunostaining has been found to be highly sensitive and specific for the diagnosis. We present a dedicated series of head and neck LGFMS, including the first reported laryngeal case, as well as a review of reported head and neck cases. The surgical pathology archives of our three institutions were searched for cases of LGFMS arising within the head and neck, and four cases were identified. The H&E slides were reviewed, and immunohistochemistry were performed for pancytokeratin, p63, p40, EMA, S100 protein, β-catenin, actin, CD34, and MUC4. The patients were 6, 43, 45, and 73 years old (mean 41.8 years) and included three males and one female. The tumors were located in the posterior cervical spine, facial skin, mandible, and larynx. The tumors were treated with surgical excision, and all four had histologic features typical for LGFMS including alternating myxoid and fibrous areas with prominent curvilinear vasculature. All tumors were MUC4 positive (100%), 2/4 (50%) were p63 positive, 1/4 (25%) showed focal EMA positivity; all 4 were negative for pancytokeratin, p40, S100 protein, β-catenin, actin, and CD34. LGFMS is a low grade sarcoma that rarely develops in the head and neck. Due to its rarity, a pathologist may not consider LGFMS in the differential diagnosis of spindle cell neoplasms within the head and neck. Immunohistochemical staining is helpful, but stains should be selected carefully to avoid misdiagnosis.

DOG1 is a highly sensitive marker for gastrointestinal stromal tumor (GIST) and is in the routine diagnostic antibody repertoire of many surgical pathology laboratories. Moreover, GIST is well recognized by both pathologists and clinicians in the differential diagnosis of intra-abdominal and pelvic neoplasms. Low-grade fibromyxoid sarcoma (LGFMS) is, however, much less frequently anticipated, particularly when occurring at unusual sites, because of its rarity and bland histology, particularly on core biopsy. We describe a case of a 53-year-old male with a large pelvic and pararectal mass, which on biopsy showed a moderately cellular spindle cell neoplasm within fibrous stroma. Immunohistochemistry at the referring center showed diffuse and strong expression of DOG1 with negativity for other markers. After referral to a tertiary center, repeat DOG1 immunohistochemistry again showed diffuse expression, but MUC4 was also positive, and this was confirmed to be LGFMS, harboring FUS-CREB3L2 fusion transcripts by reverse transcription-polymerase chain reaction and FUS rearrangement with fluorescence in situ hybridization. In view of this we assessed DOG1 expression in 10 other LGFMS (all MUC4 positive, and 9 molecularly confirmed to harbor FUS-CREB3L2 fusion transcripts and/or FUS or EWSR1 gene rearrangement), of which 5 showed DOG1 expression in up to 75% of tumor cells, varying in intensity from weak to strong. While LGFMS and GIST are generally morphologically dissimilar, less typical variants of each exist, and both can contain bland spindled cells within fibrous stroma. As the morphologic spectrum of LGFMS is wide, and as it can occur in unusual sites and may not be well recognized by general pathologists and non-soft tissue pathologists, we highlight the potential for diagnostic confusion with GIST owing to aberrant DOG1 expression. This is clinically pertinent, as the management and prognosis of these 2 neoplasms differs significantly.

BACKGROUND: Epithelial cells in malignant conditions release DNA into the extracellular compartment. Cell free DNA of tumor origin may act as a ligand of DNA sensing mechanisms and mediate changes in epithelial-stromal interactions.
AIMS: To evaluate and compare the potential autocrine and paracrine regulatory effect of normal and malignant epithelial cell-related DNA on TLR9 and STING mediated pathways in HT-29 human colorectal adenocarcinoma cells and normal fibroblasts.
MATERIALS AND METHODS: DNA isolated from normal and tumorous colonic epithelia of fresh frozen surgically removed tissue samples was used for 24 and 6 hour treatment of HT-29 colon carcinoma and HDF-α fibroblast cells. Whole genome mRNA expression analysis and qRT-PCR was performed for the elements/members of TLR9 signaling pathway. Immunocytochemistry was performed for epithelial markers (i.e. CK20 and E-cadherin), DNA methyltransferase 3a (DNMT3a) and NFκB (for treated HDFα cells).
RESULTS: Administration of tumor derived DNA on HT29 cells resulted in significant (p<0.05) mRNA level alteration in 118 genes (logFc≥1, p≤0.05), including overexpression of metallothionein genes (i.e. MT1H, MT1X, MT1P2, MT2A), metastasis-associated genes (i.e. TACSTD2, MACC1, MALAT1), tumor biomarker (CEACAM5), metabolic genes (i.e. INSIG1, LIPG), messenger molecule genes (i.e. DAPP, CREB3L2). Increased protein levels of CK20, E-cadherin, and DNMT3a was observed after tumor DNA treatment in HT-29 cells. Healthy DNA treatment affected mRNA expression of 613 genes (logFc≥1, p≤0.05), including increased expression of key adaptor molecules of TLR9 pathway (e.g. MYD88, IRAK2, NFκB, IL8, IL-1β), STING pathway (ADAR, IRF7, CXCL10, CASP1) and the FGF2 gene.
CONCLUSIONS: DNA from tumorous colon epithelium, but not from the normal epithelial cells acts as a pro-metastatic factor to HT-29 cells through the overexpression of pro-metastatic genes through TLR9/MYD88 independent pathway. In contrast, DNA derived from healthy colonic epithelium induced TLR9 and STING signaling pathway in normal fibroblasts.

BBF2H7 is an endoplasmic reticulum (ER)-resident transmembrane basic leucine zipper (bZIP) transcription factor that is cleaved at the transmembrane domain by regulated intramembrane proteolysis in response to ER stress. The cleaved cytoplasmic N-terminus containing transcription activation and bZIP domains translocates into the nucleus to promote the expression of target genes. In chondrocytes, the cleaved luminal C-terminus is extracellularly secreted and facilitates proliferation of neighboring cells through activation of Hedgehog signaling. In the present study, we found that Bbf2h7 expression levels significantly increased by 1.070-2.567-fold in several tumor types including glioblastoma compared with those in respective normal tissues, using the ONCOMINE Cancer Profiling Database. In some Hedgehog ligand-dependent cancer cell lines including glioblastoma U251MG cells, the BBF2H7 C-terminus was secreted from cells into the culture media and promoted cancer cell proliferation through activation of Hedgehog signaling. Knockdown of Bbf2h7 expression suppressed the proliferation of U251MG cells by downregulating Hedgehog signaling. The impaired cell proliferation and Hedgehog signaling were recovered by addition of BBF2H7 C-terminus to the culture medium of Bbf2h7-knockdown U251MG cells. These data suggest that the secreted luminal BBF2H7 C-terminus is involved in Hedgehog ligand-dependent cancer cell proliferation through activation of Hedgehog signaling. Thus, the BBF2H7 C-terminus may be a novel target for the development of anticancer drugs.

Gene fusions are neoplasia-associated mutations arising from structural chromosomal rearrangements. They have a strong impact on tumor development and constitute important diagnostic markers. Malignant soft tissue tumors (sarcomas) constitute a heterogeneous group of neoplasms with >50 distinct subtypes, each of which is rare. In addition, there is considerable morphologic overlap between sarcomas and benign lesions. Several subtypes display distinct gene fusions, serving as excellent biomarkers. The development of methods for deep sequencing of the complete transcriptome (RNA-Seq) has substantially improved the possibilities for detecting gene fusions. With the aim of identifying new gene fusions of biological and clinical relevance, eight sarcomas with simple karyotypes, ie, only one or a few structural rearrangements, were subjected to massively parallel paired-end sequencing of mRNA. Three different algorithms were used to identify fusion transcripts from RNA-Seq data. Three novel (KIAA2026-NUDT11, CCBL1-ARL1, and AFF3-PHF1) and two previously known fusions (FUS-CREB3L2 and HAS2-PLAG1) were found and could be verified by other methods. These findings show that RNA-Seq is a powerful tool for detecting gene fusions in sarcomas but also suggest that it is advisable to use more than one algorithm to analyze the output data as only two of the confirmed fusions were reported by more than one of the gene fusion detection software programs. For all of the confirmed gene fusions, at least one of the genes mapped to a chromosome band implicated by the karyotype, suggesting that sarcomas with simple karyotypes constitute an excellent resource for identifying novel gene fusions.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare soft tissue tumor exhibiting considerable morphologic overlap with low-grade fibromyxoid sarcoma (LGFMS). Moreover, both SEF and LGFMS show MUC4 expression by immunohistochemistry. While the majority of LGFMS cases are characterized by a FUS-CREB3L1 fusion, both FUS-CREB3L2 and EWSR1-CREB3L1 fusions were recently demonstrated in a small number of LGFMS and SEF/LGFMS hybrid tumors. In contrast, recent studies pointed out that SEF harbor frequent EWSR1 rearrangements, with only a minority of cases showing FUS-CREB3L2 fusions. In an effort to further characterize the molecular characteristics of pure SEF and hybrid SEF/LGFMS lesions, we undertook a clinicopathologic, immunohistochemical and genetic analysis of a series of 10 SEF and 8 hybrid SEF/LGFMS tumors. The mortality rate was similar between the two groups, 44% within the pure SEF group and 37% in the hybrid SEF/LGFMS with a mean overall follow-up of 66 months. All but one pure SEF and all hybrid SEF/LGFMS-tested cases showed MUC4 immunoreactivity. The majority (90%) of pure SEF cases showed EWSR1 gene rearrangements by fluorescence in situ hybridization with only one case exhibiting FUS rearrangement. Of the nine EWSR1 positive cases, six cases harbored CREB3L1 break-apart, two had CREB3L2 rearrangement (a previously unreported finding) and one lacked evidence of CREB3L1/2 abnormalities. In contrast, all hybrid SEF/LGFMS tumors exhibited FUS and CREB3L2 rearrangements. These results further demarcate a relative cytogenetic dichotomy between pure SEF, often characterized by EWSR1 rearrangements, and hybrid SEF/LGFMS, harboring FUS-CREB3L2 fusion; the latter group recapitulating the genotype of LGFMS.

BACKGROUND: Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft tissue tumor typically affecting young to middle-aged adults. Despite its otherwise benign histologic appearance and indolent nature, it can have fully malignant behavior, and recurrence and metastasis may occur even decades later.
CASE HISTORY: We report a case of LGFMS in the left lower leg of a 5-year-old Japanese boy. A magnetic resonance imaging (MRI) uncovered a well-demarcated intra-gastrocnemial tumor measuring 27 × 20 mm with a slightly high intensity on T1WI and heterogeneously high intensity on T2WI. Histologically, the tumor was composed of bland spindle-shaped cells with a whorled growth pattern. The tumor stroma was variably hyalinized and fibromyxoid with arcades of curvilinear capillaries and arterioles with associated perivascular fibrosis. Although LGFMS is known to affect children under 18 years of age, it is extremely rare in infants and children under 5 years of age. Despite the young age, this patient was accurately diagnosed by the typical histology and the detection of a FUS-CREB3L2 gene fusion.
CONCLUSION: Although LGFMS in children tends to be located superficially, this case presented with an intramuscular tumor in the region of the gastrocnemius. To the best of our knowledge, this is the first case of deep LGFMS arising in a child younger than 5 years of age. The patient is still alive with no evidence of the disease 4 months after diagnosis.
VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_163.

BACKGROUND: The diagnosis of the follicular variant of papillary thyroid carcinoma (FVPTC) is increasingly common. Recent studies have suggested that FVPTC is heterogeneous and comprises multiple tumor types with distinct biological behaviors and underlying genetics.
OBJECTIVES: The purpose of this work was to identify the prevalence of mutations and gene fusions in known oncogenes in a panel representative of the common spectrum of FVPTC diagnosed at an academic medical center and correlate the clinical and pathological features obtained at the initial diagnosis with the tumor genotype.
MATERIALS AND METHODS: We performed SNaPshot genotyping on a panel of 129 FVPTCs of ≥1 cm for 90 point mutations or small deletions in known oncogenes and tumor suppressors and identified gene fusions using an anchored multiplex PCR assay targeting a panel of rearranged oncogenes.
RESULTS: We identified a mutation or gene fusion in 70% (89 of 127) of cases. Mutations targeting the RAS family of oncogenes were the most frequently observed class of alterations, present in 36% (46 of 127) of cases, followed by BRAF mutation, present in 30% (38 of 127). We also detected oncogenic rearrangements not previously associated with FVPTC, including TFG-ALK and CREB3L2-PPARγ. BRAF mutation was significantly associated with unencapsulated tumor status.
CONCLUSIONS: These data support the hypothesis that FVPTC is composed of distinct biological entities, with one class being identified by BRAF mutation and support the use of clinical genotyping assays that detect a diverse array of rearrangements involving ALK and PPARγ. Additional studies are necessary to identify genetic drivers in the 30% of FVPTCs with no known oncogenic alteration and to better predict behavior in tumors with known genotypes.

We present the case of a 6-year-old boy with a deceptively bland spindle cell renal neoplasm found to harbor the EWSR1-CREB3L1 gene fusion. This fusion has recently been described as a variant translocation in low-grade fibromyxoid sarcoma (LGFMS), a tumor more typically characterized by a recurrent t(7;16) chromosomal translocation, resulting in the fusion of FUS and CREB3L2 genes. LGFMS is an indolent tumor with late metastatic potential and a propensity for long-term disease recurrence. The tumor is rare in children, with only 33 published cases. In the pediatric population, it has not previously been reported arising in the kidney.

Sclerosing epithelioid fibrosarcoma (SEF) and low-grade fibromyxoid sarcoma (LGFMS) are 2 distinct types of sarcoma, with a subset of cases showing overlapping morphologic and immunohistochemical features. LGFMS is characterized by expression of the MUC4 protein, and about 90% of cases display a distinctive FUS-CREB3L2 gene fusion. In addition, SEF is often MUC4 positive, but is genetically less well studied. Fluorescence in situ hybridization (FISH) studies have shown involvement of the FUS gene in the majority of so-called hybrid LGFMS/SEF and in 10% to 25% of sarcomas with pure SEF morphology. In this study, we investigated a series of 10 primary tumors showing pure SEF morphology, 4 cases of LGFMS that at local or distant relapse showed predominant SEF morphology, and 1 primary hybrid LGFMS/SEF. All but 1 case showed diffuse expression for MUC4. Using FISH, reverse transcription polymerase chain reaction, and/or mRNA sequencing in selected cases, we found recurrent EWSR1-CREB3L1 fusion transcripts by reverse transcription polymerase chain reaction in 3/10 pure SEF cases and splits and deletions of the EWSR1 and/or CREB3L1 genes by FISH in 6 additional cases. All 5 cases of LGFMS with progression to SEF morphology or hybrid features had FUS-CREB3L2 fusion transcripts. Our results indicate that EWSR1 and CREB3L1 rearrangements are predominant over FUS and CREB3L2 rearrangements in pure SEF, highlighting that SEF and LGFMS are different tumor types, with different impacts on patient outcome.

Low-grade fibromyxoid sarcoma (LGFMS) is an uncommon sarcoma with a deceptively bland-looking morphology that disguises its malignant clinical behavior. It shows distinctive chromosomal translocations resulting in fusion of FUS with the CREB3L2 gene in most cases and CREB3L1 in rare cases. Thus molecular studies are particularly helpful in the diagnosis of this bland-looking sarcoma. We report 2 cases of LGFMS serendipitously found to harbor a novel alternative EWSR1-CREB3L1 gene fusion, as confirmed by DNA sequencing of reverse transcriptase-polymerase chain reaction products and fluorescence in situ hybridization. One patient was a child who presented with a subcutaneous nodule on the lower leg, and the other was a middle-aged woman who had a mass lesion over the proximal thigh. Morphologically, one case showed a spindle cell tumor with hyalinization and giant rosettes, whereas the other showed classical histology of LGFMS with focal metaplastic bone formation. Immunostaining for MUC4 showed extensive positive staining. Our findings therefore expand the spectrum of gene fusions that characterize LGFMS and suggest that the EWSR1 gene may substitute for the function of FUS in gene fusions of sarcoma.

We report the unusual cardiac localization of a primary low-grade fibromyxoid sarcoma of the right ventricle in a 57-year-old woman. Histological examination revealed a prevalent myxoid appearance with whorling growth pattern of small or spindle cells with bland features alternating with rare more collagenous hypocellular areas with rare atypical cells. Genomic polymerase chain reaction of genomic DNA revealed the typical FUS/Creb3L2 fusion gene products typical of low-grade fibromyxoid sarcoma. The tumor was surgically removed and recurred after 7 years as high-grade pleomorphic sarcoma. The patient died 6 months after the clinical manifestation of recurrence. Low-grade fibromyxoid sarcoma of soft tissues is a rare, distinctive variant of fibrosarcoma-typically arising in deep soft tissue of lower extremities and trunk-that rarely metastasizes. Clinically, low-grade fibromyxoid sarcoma is characterized by a longer survival rate compared to other sarcomas, suggesting its consideration in the differential diagnosis of cardiac tumors with a myxoid appearance.

Sclerosing epithelioid fibrosarcoma (SEF) is a rare aggressive fibroblastic neoplasm composed of cords of epithelioid cells embedded in a dense collagenous stroma. The reported immunophenotype of SEF is nonspecific. Some SEF cases show morphologic and molecular overlap with low-grade fibromyxoid sarcoma (LGFMS), suggesting a relationship between these tumor types. MUC4 has recently been identified as a sensitive and specific marker for LGFMS; MUC4 expression was also observed in 2 tumors with hybrid features of SEF and LGFMS. We investigated MUC4 expression in SEF and other epithelioid soft tissue tumors to determine (1) the potential diagnostic utility of MUC4 for SEF and (2) the association between MUC4 expression and FUS rearrangement in SEF. Whole sections of 180 tumors were evaluated: 41 cases of SEF (including 29 "pure" SEF and 12 hybrid LGFMS-SEF), 20 epithelioid sarcomas, 11 clear cell sarcomas, 11 metastatic melanomas, 10 perivascular epithelioid cell tumors, 10 alveolar soft part sarcomas, 10 epithelioid angiosarcomas, 10 epithelioid hemangioendotheliomas, 10 epithelioid gastrointestinal stromal tumors, 10 myoepithelial carcinomas, 17 ossifying fibromyxoid tumors, 10 leiomyosarcomas, and 10 biphasic synovial sarcomas. Immunohistochemical analysis was performed after antigen retrieval using a mouse anti-MUC4 monoclonal antibody. Fluorescence in situ hybridization (FISH) was performed on 33 SEF cases using FUS break-apart probes. A subset of cases was also evaluated for EWSR1 and CREB3L2/L1 rearrangements by FISH. Strong diffuse cytoplasmic staining for MUC4 was observed in 32 of 41 (78%) cases of SEF, including all 12 hybrid tumors. FUS rearrangement was detected in 8 of 21 (38%) MUC4-positive cases of SEF with successful FISH studies. The prevalence of FUS rearrangement was similar in hybrid LGFMS-SEF (2 of 6; 33%) and SEF without an LGFMS component (6 of 15; 40%). FUS rearrangement was not detected in any cases of MUC4-negative SEF. Two hybrid tumors had both EWSR1 and CREB3L1 rearrangements. MUC4 expression was also seen in 9 of 10 (90%) biphasic synovial sarcomas, predominantly in the glandular component. All other tumor types were negative for MUC4, apart from focal reactivity in 5 ossifying fibromyxoid tumors, 2 epithelioid gastrointestinal stromal tumors, and 1 myoepithelial carcinoma. MUC4 is a sensitive and relatively specific marker for SEF among epithelioid soft tissue tumors. MUC4 expression occurs more frequently than FUS rearrangement in SEF. The finding of EWSR1 and CREB3L1 rearrangements in 2 cases of hybrid LGFMS-SEF suggests that SEFs are genetically heterogenous. MUC4-positive SEFs with FUS rearrangement are likely closely related to LGFMS. MUC4-positive SEFs that lack FUS rearrangement may be related to LGFMS but could have alternate fusion partners, including EWSR1. SEF without MUC4 expression may represent a distinct group of tumors. MUC4 expression correlates with glandular epithelial differentiation in biphasic synovial sarcoma and is very limited in other epithelioid soft tissue tumors.

Low-grade fibromyxoid sarcoma is a rare soft tissue sarcoma of fibroblastic differentiation characterized by a deceptively benign morphologic appearance with almost consistent MUC4 expression and recurrent chromosomal translocations, t(7;16)(q34;p11) and t(11;16)(p11;p11), resulting in the FUS-CREB3L2 and FUS-CREB3L1 fusion genes, respectively. A subset of the tumors show peculiar histologic features, designated as giant rosettes, and were formerly referred to as hyalinizing spindle cell tumor with giant rosettes. We herein report a case of low-grade fibromyxoid sarcoma showing the presence of numerous giant rosettes, with and without collagenous centers, distributed throughout the lesion and unusual rim-like heterotopic ossification. Such a case might present a diagnostic challenge. The diagnosis of the tumor was confirmed by positive immunoreactivity to MUC4 and the FUS-CREB3L2 fusion detected by molecular testing using formalin-fixed, paraffin-embedded tissue. This case, which has such unusual clinicopathologic features, would help to further expand our knowledge regarding the morphologic diversities of low-grade fibromyxoid sarcoma.

Low-grade fibromyxoid sarcoma was first described more than 20 years ago. Subsequently, it was discovered to carry the recurrent chromosomal translocation t(7;16)(q33;p11) encoding a FUS-CREB3L2 fusion oncoprotein. Molecular tests for this pathognomonic gene fusion can confirm the identity of histologic variants (such as hyalinizing spindle cell tumor with giant rosettes) and suggest that some cases of sclerosing epithelioid fibrosarcoma may represent a high-grade version of this entity. We present a case of an ossifying tumor of the perineum that required an open biopsy and fluorescent in situ hybridization testing for FUS and CREB3L2 for diagnosis as a variant of low-grade fibromyxoid sarcoma. Subsequent excision revealed characteristic areas with collagen rosettes as well as foci of heterotopic ossification. Significant ossification, which is well documented in entities such as synovial sarcoma, ossifying fibromyxoid tumor, and extraskeletal osteosarcoma, has not been reported previously in low-grade fibromyxoid sarcoma. This case demonstrates the value of having a distinctive confirmatory molecular pathology test for diagnosis and expands our knowledge of the histologic variants possible in low-grade fibromyxoid sarcoma.

PURPOSE: Low-grade fibromyxoid sarcoma (LGFMS) is typically characterized by the specific translocation t(7;16)(q33;p11) and the corresponding fusion gene FUS-CREB3L2. The present study aimed to extract LGFMS-specific, and putatively FUS-CREB3L2-dependent, gene expression patterns to learn more about the pathogenesis of this tumor.
EXPERIMENTAL DESIGN: We carried out single nucleotide polymorphism (SNP) and global gene expression array analyses, and/or immunohistochemical (IHC) analyses on 24 LGFMS tumor biopsies. Tumor types that are important differential diagnoses to LGFMS were included as comparison in the gene and protein expression analyses. In addition, cells that stably expressed FUS-CREB3L2 were analyzed with gene expression array and the influence of FUS-CREB3L2 on gene expression was investigated in vitro.
RESULTS: The SNP array analysis detected recurrent microdeletions in association with the t(7;16) chromosomal breakpoints and gain of 7q in cases with ring chromosomes. Gene expression analysis clearly distinguished LGFMS from morphologically similar tumors and MUC4 was identified as a potential diagnostic marker for LGFMS by gene expression and IHC analysis. FOXL1 was identified as the top upregulated gene in LGFMS and CD24 was upregulated in both LGFMS tumors and FUS-CREB3L2 expressing cells. FUS-CREB3L2 was capable of activating transcription from CD24 regulatory sequences in luciferase assays, suggesting an important role for the upregulation of this gene in LGFMS.
CONCLUSIONS: The gene expression profile of LGFMS is distinct from that of soft tissue tumors with similar morphology. The data could be used to identify a potential diagnostic marker for LGFMS and to identify possible FUS-CREB3L2 regulated genes.

Low-grade fibromyxoid sarcoma (LGFMS) is a distinctive fibroblastic neoplasm that is characterized by alternating collagenous and myxoid areas, deceptively bland spindle cell morphology, a whorling architecture, and a t(7;16) translocation involving FUS and CREB3L2. Owing to variable morphology and a lack of discriminatory markers, LGFMS can be difficult to distinguish from benign mesenchymal tumors and other low-grade sarcomas. Gene expression profiling has identified differential upregulation of the mucin 4 (MUC4) gene in LGFMS compared with histologically similar tumors. MUC4 is a transmembrane glycoprotein that functions in cell growth signaling pathways; aberrant MUC4 expression has been reported in various carcinomas. We investigated MUC4 protein expression by immunohistochemistry in LGFMS and in other soft tissue tumors to determine the potential diagnostic use of this novel marker. Whole-tissue sections of 309 tumors were evaluated: 49 LGFMSs (all with FUS gene rearrangement confirmed by fluorescence in situ hybridization), 40 soft tissue perineuriomas, 40 myxofibrosarcomas, 20 cellular myxomas, 20 solitary fibrous tumors, 20 low-grade malignant peripheral nerve sheath tumors, 20 cases of desmoid fibromatosis, 20 neurofibromas, 20 schwannomas, 20 monophasic synovial sarcomas, 20 cases of dermatofibrosarcoma protuberans, 10 myxoid liposarcomas, and 10 extraskeletal myxoid chondrosarcomas. The LGFMS cases included 7 with marked hypercellularity, 4 with prominent hemangiopericytoma-like vessels, 3 with giant collagen rosettes, 3 with epithelioid morphology, 2 with focal nuclear pleomorphism, and 2 with areas of sclerosing epithelioid fibrosarcoma. All 49 LGFMS cases (100%) showed cytoplasmic staining for MUC4, which was usually diffuse and intense. All the other tumor types were negative for MUC4, apart from 6 (30%) monophasic synovial sarcomas. In conclusion, MUC4 is a highly sensitive and quite specific immunohistochemical marker for LGFMS, and can be helpful to distinguish this tumor type from histologic mimics.

BACKGROUND: Low-grade fibromyxoid sarcoma (LGFMS) is a rare soft-tissue neoplasm with a deceptively benign histological appearance. Local recurrences and metastases can manifest many years following excision. The FUS-CREB3L2 gene translocation, which occurs commonly in LGFMS, may be detected by reverse-transcriptase polymerase chain reaction (RT-PCR) and fluorescence in situ hybridisation (FISH). We assessed the relationship between clinical outcome and translocation test result by both methods.
METHODS: We report genetic analysis of 23 LGFMS cases and clinical outcomes of 18 patients with mean age of 40.6 years. During follow-up (mean 24.8 months), there were no cases of local recurrence or metastasis. One case was referred with a third recurrence of a para-spinal tumour previously incorrectly diagnosed as a neurofibroma.
RESULTS: Results showed 50% of cases tested positive for the FUS-CREB3L2 translocation by RT-PCR and 81.8% by FISH, suggesting FISH is more sensitive than RT-PCR for confirming LGFMS diagnosis. Patients testing positive by both methods tended to be younger and had larger tumours. Despite this, there was no difference in clinical outcome seen during short and medium-term follow-up.
CONCLUSIONS: RT-PCR and FISH for the FUS-CREB3L2 fusion transcript are useful tools for confirming LGFMS diagnosis, but have no role in predicting medium-term clinical outcome. Due to the propensity for late recurrence or metastasis, wide excision is essential, and longer-term follow-up is required. This may identify a difference in long-term clinical outcome between translocation-positive and negative patients.

Low-grade fibromyxoid sarcoma (LGFMS) is a rare, typically deep-seated soft tissue neoplasm with deceptively bland cytology and metastatic potential. A t(7;16)(q34;p11) translocation, yielding a FUS/CREB3L2 fusion gene, has been identified in approximately 80%-90% of deep soft tissue LGFMS. Cutaneous fibromyxoid neoplasms occur not infrequently; dermatopathologists rarely consider LGFMS in the differential diagnosis, as this lesion is uncommon in the skin. We identified a group of superficial LGFMS and a spectrum of other cutaneous fibromyxoid neoplasms and performed fluorescence in situ hybridization (FISH) to assess the frequency of FUS rearrangement. FISH for the chromosomal rearrangement of FUS (16p11), using a dual-color, break-apart probe (Abbott Molecular/Vysis, Des Plaines, IL), was performed on formalin-fixed paraffin-embedded tissue sections from superficial LGFMS (n = 6), myxomas (n = 10), and myxofibrosarcoma/myxoid malignant fibrous histiocytomas (myxoid MFH) (n = 5). One hundred nonoverlapping tumor nuclei per case were evaluated for either fused (normal) or split (translocated) signals. Of the LGFMS, 4 of 6 (67%) showed a rearrangement of FUS (range: 72%-80% positive nuclei per 100 nuclei). The other neoplasms within the differential diagnosis were devoid of any rearrangement involving FUS (range: 0%-2% positive nuclei per 100 nuclei). Our observed frequency of FUS rearrangement in superficial LGFMS is consistent with those published in the literature for more deeply seated lesions. When applied to suspicious superficial myxoid or fibromyxoid neoplasms, the FUS FISH probe in formalin-fixed paraffin-embedded tissue can be a useful ancillary technique for diagnosis of this uncommon and deceptively bland tumor.